Line finder dual-allotter system



Oct. 20, 1953 F. KssLL-Rr LINE FINDER DUAL-ALLOTTER SYSTEM Filed April 13, 1948 8 Sheets-Sheet l mun-ZE OPOmJm-m F. KESSLER LINE FINDER DUAL-ALLOTTER SYSTEM Oct. 20, 1953 8 Sheets-Sheet 2 Filed April 13, 1948 ml.. v v lo movl l N N hs S ONWOIH. old WIN mN IN PN wIN wm 1 .s N .PN w. O .5 Mu

5, JNVENTOR.

FRANK KESSLER Eywll ATTORNEY Oct. 20, 1953 F. KEssLER LINE FINDER DUAL-ALLOTTER SYSTEM s sheets-sheet s Filed April 1.3, 1948 Elli +1 INVENTOR.

Nv @M004 l FRANK KEssLER ww Timm/l ATTORNEY EWEQEIIWEI Oct. 20, 1953 F. KEssLER VLNE FINDER DUAL AI .LOTTER SYSTEM 8 Sheets-Sheet 4 Filed April 15,1948

INVENTOR.

FRANK KESSLER WFM ATTORNEY Oct.v20, 1953 F". KEssLER f 2,656,416

LINE FINDER DUAL-ALLOTTER SYSTEM FRANK KESSLER Y www fr WMM ATTORNEY Oct. 20, 1953 F. KEssLER 2,556,416

'LINE FINDER DUAL-ALLOTTER SYSTEM Filed April 15, 194e. 1 s sheets-sheet e (D l JNVENTOR. FRANK KESSLER Tf M ATTORNEY Oct. 20, 1953 F. KEssLER 2,656,416

LINE FINDER DUAL-ALLOTTER SYSTEM Filed April 15, 194e s' sheets-sheet 'I PE 4Q 0: V r E i g c. u I Q VI f LL. 1.

I' HI F v fg I J' N l I Y f g 4 Lu HBWU.

INVENTolg. L?, FRANK KESSLER BY MLTM A T TORNE Y Oct. 20, 1 953 F. KEssLER 2,656,416

LINE FINDER DUAL-ALLOTTER SYSTEM Filed April 15, 1948 a sheets-sheep' 8 A AINVENTOR.

FRANK KESSLER BY Wwf Ewan ATTORNEY Patented Oct. 20, 1953 LNE FINDER DUAL-ALLOTTER SYSTEM Frank Kessler, Rochester, N. Y., assignor to Stromberg-Carlson Company, a corporation of New York Application April 13, 1948, Serial No. 20,745

21 Claims.

This invention relates in general to automatic telephone systems, but more particularly to such systems in which line nders are employed to connect an allotted line nder switch with a calling line and the principal object of the invention, briefly stated, is the provision of new and improved circuit refinements in nder switch systems, the improvements tending to make the system more reliable, to give uniform high quality service and to make it cheaper to install and maintain.

another object of the present invention is a new and improved dual allotter arrangement in which one allotter normally controls the operation of an allotted iinder and which is arranged to lock itself out of service and switch a calling line to its companion allotter for allotting another line finder, in the event that the first allotted line nder fails to iind the calling line and clear out the first mentioned allotter within a predetermined time.

A s a further object of the present invention, the allotter and its companion allotter are Iconnected to a timing device which operates within a predetermined time, in case the allotter fails to kick off and select a new line iinder, to bring in an alarm signal and lock the allotter out of service until the exchange attendant operates a reset key, the calls normally handled by the allotter being handled by-the companion allotter during this locked out condition.

ln the embodiment of my invention, I propose to use a line iinder switch of the two motion type, i. e., a switch whose wipers are moved first in a primary or X direction to select the desired level and then in a secondary or Y direction to the desired bank contacts in the level. Furthermore, I propose to use a nder switch of the directive type, that is, a switch which is driven in its primary or X direction and in its secondary or Y direction by an external sender mechanism, rather than a finder arrangement of the self interrupted type. This sender mechanism is associated with the common allotter circuit.

Another object of my invention is to provide circuit arrangements whereby if the finder switch which operates in response to a call from a calling line in the group of lines from which it is'iirst seized fails to connect with that line, due to either a mechanical or electrical defect in the finder or the allotter equipment, the allotter involved will be locked out and the finder involved will be released, after which another finder in the common group will be controlled by the second or companion allotter to connect with the calling line.

Another object of my invention is to provide an all iinders busy relay in the control equipment, Ythat relay remaining energized as long as an idle nder remains in the group controlled by the equipment. When the last nder in the group is used, the all finders busy relay releases and removes the control equipment from service so that al1 calls from either group of lines are now prevented from operating any of the apparatus in the allotter -or finder groups associated with this group of lines. During this condition a busy tone is applied to any calling line as an indication that there is no idle equipment available at this time.

Still another object of my invention is the pro- Vvision of an overflow arrangement in the line finder switches, whereby 11 lines may be provided in each level of each line iinder switch. This is possible in the X-Y switch system to which applicants invention is applied because the X-Y switch is so designed mechanically that it has access to 11 sets of bank contacts in each level. This arrangement of the X-Y switch is pointed out in the pending application Serial No. 743,415, filed April 23, 1947, and assigned to the same assignee as the present invention, now Patent No. 2,567,650. A

A further object of the present invention is the provision of a time delay arrangement in connection with the `11th secondary or Y step of the iinder switches, whereby this llthstep may provide an 11th line or trunk on each level. Normally this 11th step in the Y direction is an overow position and, in the present disclosure, the

overflow mechanism functions to cause the release of the circuits if the switch advances to the 11th step and no trunk is connected to the bank terminals ofY this step. In the event that this 11th step is provided with a trunk line, then the selection of the trunk within a predetermined time will prevent the kick-off operation from the overow contacts. rIhis feature will be described in detail in the following description. Another feature of the present invention is the provision of toll lines-in the normal level of the nderswitch multiple, calls from these toll lines being effective to operate an allotted line finder in its secondary or Y direction only in the normal level for selecting calling toll lines. Such an arrangement makes it possible to provide 110 local lines and Il toll lines, or a total of 121 lines in the finder switch. bank multiple. This is bacause l1 lines are provided on each of the l0 levelsr requiring an X step and an additional l1 lines ing the operation of the system will be a help in understanding the detailed description which follows.

The circuits disclosed provide for iinders, allotters and lines for a group cf subscribers lines (11G lines for example) and a group of trunk lines (ll for example).

Both the primary (X) and secondary (Y) magnets of each line finder are `operated from a regulated speed and per cent make-break impulse source in each allotter.

Generation of the impulses for driving the X and Y magnets is provided in each allotter, with an arrangement whereby the allotter is stepped to the next nnder in case the X or operation is advanced to an overflow position, when this posi, tion is not used for a line or trunk line. The circuits are so arranged .that a start condition from a trunk or toll line has preference over any subscribers line start condition, or as many trunk calls as are stored at that time.

Two allotters form an AB allotter combination and are provided for each group, with means for omitting one if not required and with means whereby each allotter may be timed out and transfer-red to the other allotter. After this first time out operation, an additional time out operation is effective to step the other allotter to the next idle nder.

Starting potential from lines in the odd levels of the finders operate by way of the A allotter and from lines in the even levels of the nders by way o f the B allotter. When either allotteil transfers to the other, the common start and marking leads are connected together so that each nnder functions to iind on all levels.

Reset keys are provided in each allotter for restoring to normal an allotter which has timed itself out.

The banks of the allotters are arranged in reverse order to prevent the two allotters from falling into step. With this arrangement, when the two allotters get in step at a particular point, the kick off operation functions to kick both allotters away from this same finder terminal, but since the bank connections are in reverse order the first allotter will be advanced from one link say #2 to the next link say #1, while the companion allotter will be advanced from link #2 to link #3 for example.

Further features of the invention relate to the particular arrangement of the `circuit elements whereby the above and additional features are attained.

The novel features believed to be characteristie of the invention are set forth in the appended claims. The invention, both as to its organization and method of operation, together with further objects and advantages thereof will be best understood by reference to the following specification taken in connection with the accompanying drawings in which Figs. 1r to 6A incluy sive, 9 and 1Q taken together and arranged as indicated in Fig. "t and with correspondingly numbered or lettered lines inalignment illustrate an allotter-finder arrangement having incor- Dorated -therein the features of the. invention briefly outlined above. Fig.. 8 shows the arrange-A ment of toll line in the normal level.

For the purpose of simplifying the illustrations andfacilitating the explanation, the various parts and circuits constituting the embodiment of the invention have been shown diagrammatically and certain conventional illustrations have. been employed.' the drawings having been made more with the purpose of making it easy to understand the principles and mode of operation than with the idea of illustrating the specific construction and arrangement of parts that would be actually employed in practice. For example, the various relays and their contacts are illustrated in a conventional manner, with all of the contacts controlled by a particular relay being associated with this relay by means of a dashed line. The ATB relay illustrated in Fig. 3 has most of its contacts shown in association with this relay by means of the dashed line, but Jthis relay is the exception to the above rule in that there are three additional sets of contacts associated with the ATB relay and illustrated in Fig. 5, with the ATB relay being blocked in and a notation provided to the eifect that this is the ATB relay shown in the circuit of Fig. 3. This is the only case Where contacts of a relay are not shown associated with the relay at the location in the circuit Where the relay is controlled. The negative side of the common exchange battery is indicated by and the positive side of the eX- `change battery, which is usually grounded, is illustrated by For convenience in describing the operation of the system disclosed it will rst be assumed that a call is originated from a line in an odd level, for example line #33 illustrated as connected to sub-station A in the upper portion of Fig. 2.

When the receiver is removed at the sub-station associated Wit-h the calling line, a circuit is closed for operating line relay OLR associated with this line extending from break contact of cut oif relay OCO, tip side OT of the calling line, calling sub-station, ring side OR of the line, break contact of relay OCO, winding of relay OLR, conductor 29 and winding of link busy tone transformer LBT to This operates relay OLR for immediately making this calling line busy in the connector banks by applying at the lower inner make contact of relay OLR to sleeve conductor OS in the connector banks. Relay OLR, at its upper make contact, closes a circuit from through the winding of relay OCO to the sleeve terminal in the finder banks for marking this line as the one in the third level which is calling. At the outer lower make contact of relay OLR, (-1-) is connected to the conductor indicated level 3 for marking the level in the finder switches in which the calling line is located.

The. circuit from (-1-) applied to the level 3" conductor extends through level resistor 3R, conductor 25, break contact of allotter trunk start relay ATS, break contact of transfer relay ATF, conductor 51, normally closed make contact of all trunks busy relay ATB, conductor 59 and winding of relay AST to Relay AST operates and immediately closes a locking circuit for itself extending from the on conductor 25,

break contact of relay ATS, break contact of rel lay ATF, make contact and winding of relay AST to It will be obvious that relay ATB is maintained operated as long as there is one or more idle finders in the group, the circuit eX- tending from C+), break contact of one or more SA relays of the selectors, Y off normal contacts YON, conductor ATB, X and Y off normal contacts XONv and YON in series, break contact of start relay ST, common conductor 45 and winding of the ATB relay to YRelay AST closes a circuit for the A start failure lamp. ASTFL extendi'ng from (+L make contact of relay AST, lamp AS'IFL, conductor 36,

break contact of the B allotter transfer relay BTF and common delayed alarm circuit (so indicated), it being understood that this common circuit completes the lamp circuit by way of a slow operating device to the alarm not operating until after a sufficient time has been measured oil" to permit the normal operation of the finder and allotter circuits. If this normal operation is not completed within a predetermined time, then the alarm circuit functions to indicate to the attendant, or to ysignal a distant oice that the A allotter has failed to operate properly.

' A circuit is now closed for operating relay ASA associated with the A allotter, this circuit'extending from break contact of the A reset key, break contact of the overiiow relay OFP, make contact of relay AST, conductor 6I, break contact oi' relay AXA, conductor 60 and winding of relay ASA to Relay ASA immediately closes a locking circuit for itself extending from break contact of the A reset key, break contact of relay OFP, make contact of relay ASA, conductor 58, make contact of relay AGD (operated as will next be explained), conductor 60 and winding of relay ASA to The circuit for operating relay AGD extends from break contact of the A reset key, make contact of relay AST, conductor 65, winding of relay AGD, make contact of relay ATB, conductor 55, break contact and winding of the A allotter stepping magnet ARX to Relay AGD closes a locking circuit for itself extending from break contact of the A reset key, make contact of relay ASA, conductor 63, make contact of relay AGD, winding of relay AGD, and over the rest of the previously described operating circuit for relay AGD including the winding of magnet ARX.

The operation of relay AGD closes a priming circuit for relay AYS to render this relay fast inv its operation when the calling line is found by the line finder. This priming circuit extends from on conductor 64, from the A reset key, make contact of relay AGT, conductor 84, resistor I'lR and lower winding of relays AYS to It will be understood that the resistance of resistor HR is sufficiently high to p-revent the operation of relay AYS at this time. Furthermore, relay AGD can be operated over the above described circuit only if the A allotter is on an idle iinder link. This is because-conductor 44 will be connected to (-l-) if this allotter is not resting on an idle link, by way of a circuit 'extending from make contact of relay SA of -f the associated selector, break contact ofthe finder release magnet ZM, or through a make contact of magnet ZM if the nder is being released at this time, conductor 44, terminal and allotter brush AA and break contact of relay AGD to the point between the winding of this relay and magnet ARX, thus providing a circuit for short circuiting relay AGD and for operating magnet ARX. This advance circuit for theY A allotter stepping magnet provides a means fork preventing the operation of relay AGD if and when the allotter is stepping along .toV nd an idle link when a call is initiated. The operation of relay AGD immediately applies (-f) to the wiper and terminal AA of the A allotter for making this link busy and for stepping the B allotter 0E this particular link if this B allotter should be resting at this point when the A allotter func'- tions to handle a call. The'circuit for' stepping the B allotter may be traced from (-f-), make` contact of relay AGD, wiper and terminal AA of the A allotter, conductor 44 extending through Figs. 3, 4 and 5 to Fig. 6, through the terminal and wiper BA of the B allo-tter, break contact of relay BGD, conductor 16, make contact of relay ATB, break contact and winding of the B allotter stepping magnet BRX to The operation of relay AGD closes a circuit for operating the start relay ST of the allotted finder (Fig. 1) extending from make contact of relay AGD, break contact of relay AYS, Wiper and terminal AB, conductor '23 and winding of relay ST to The operation of relay ST closes a pre-impulse circuit for operating the calling bridge or line relay CB of the allotted link to prepare the link circuit ahead of the extension of the calling line thereto. This circuit may be traced from upper winding of relay CB of the selector, tip conductor T, upper make contact of relay ST, resistor IIR, break contact of switching relay SW, conductor R and lower winding of relay CB to Relay CB closes an obvious circuit for operating slow acting relay SA.

The circuits are now in condition for operating the pulse generating relays APA and APB in the A allotter, these relays serving to drive the allotted nder switch inl its X and Y directions for finding the calling line. Before describing the operation of the finder stepping magnets the operating circuits for the APA and APB relays will be explained. It is desirable to provide pulses of proper speed and break-make ratios for driving the stepping magnets of the finder switch. With the arrangement of the APA and APB relays shown in Fig. 3, the proper speed and ratio is obtained. Resistor |5R is variable and is connected in parallel with relay APB and adjusted to provide the proper release time of this relay, it being understood that relay ABP will be operated within a normal time interval when energized because the full battery potential is connected across its winding when pulsing operations begin. The resistor across the winding of relay APB however, renders this relay slightly slow to release.V 1 When relay AGD operates, as above described, on conductor 64 is extended through a make contact of relay AGD to conductor 84, and thence through a break contact of relay AYS to a pair of break contacts on relay APA, this circuit divides and one branch extends to the APB relay c for operating this relay At the same time that relay ABP operates the circuit is closed through the upper winding of relay APA for energizing this upper winding. At the "same time is applied -to the lower winding of relay APA for discharging-the condenser connected in series with this winding, this condenser being normally charged through the lower winding of relay APA and resistor IGR in series. Since the energizing current through the upper winding of relay APA andthe condenser discharge current through the lower winding apply potential to the left hand terminals of both of these windings andl since the windings ofV these relays are differentially connected, the relay is slightly slow to cperate. When the condenser is discharged, cur- I rent ceases to flow in the lower winding and the relay operates by means of the current in its' upper winding. p :When relay APA operates, the4 condenser' will again charge over a'clrcuit including the lower winding of this relay'and resistor IGR in parallel" Yhesite direction from the above described discharge current, consequently the two windings will be energized in aiding relation by this charging current until the condenser reaches a pre-- determined charge, thus rendering the APA relay slightly slow to release. It will be observed that the operation of relay APA disconnects grounded conductor 84 from the windings of relays APB and APA for effecting the release of these relays. Relay APB is slightly slow to release, as above described and relay APA is slightly slow to release because of the charging current from the condenser. When the APA relay next releases, the original circuits for the APA and APB relays are again completed, thus causing these relays to again operate, after which they are again released as previously described. Consequently, the APA and APB relays continue to operate and release for providing a pulse generating circuit for driving the switch stepping magnets.

The -X magnet for driving the iinder in its primary direction is energized over a circuit extending from (-1-), break contact of the reset key, break contact of relay OFP, conductor 64, make contact of relay AGD, conductor 84, make contact of relay APB, break contact of relay AXP', wiper and terminal AD of the allotter, conductor 33, winding of finder magnet XM and break contact of magnet ZM to It will be seen that each operation of the APB relay closes a driving circuit for the finder switch X magnet. In the present example the nder switch is advanced to the third (odd) level since this is the level in which the calling line is located. When this level is reached the finder switch level brush IX is in contact with the third level terminal to which conductor I 5 is connected, thus providing a stopping circuit for the lnder switch which may be traced from make contact of relay OLR of the calling line circuit, conductor l5, terminal and wiper IX, conductor 26, terminal and wiper AE of the A allotter, make contact of relay AGD, break contact of relay AYA and winding of relay AXA to Relay AXA operates and closes a locking circuitl for itself extending from break contact of the A reset key, break contact of relay OFP, make contact of relay ASA, conductor 58, make Contact of relay AGD, make contact of relay AXA, resistor 22R and winding of relay AXA to Since relay AXA is operated when magnet XM is energized to advance its level testing brush IX to the terminal of the third level, the circuits will be maintained until relay APB releases to mark the end ofthe pulse cycle. The release of relay APB opens up and releases magnet XM and since the nder is at the third level at this time a circuit is closed for operating relay AXB extending from (-1-), break contact of the A reset key, break contact of relay OFP, conductor 64. make contact of relay AGD, conductor 84, break contact of relay APB, make contact of relay AXA, break contact and winding of relay AXB to Relay AXB immediately closes a locking circuit for itself extending from on conductor 84, make contact and winding of relay AXB to The operation of relay AXB opens up allotter wiper AD for opening up the circuit to the finder X magnet, thus stopping the operation of the finder at the marked level.

It is now in order to cange the switch operating circuit from theX magnet to the Y magnet,

since the primary selection has been made. Due to the fact that the wipers of theinder switch are atthe proper level the X stepping operation is completed. AIt is advisable to use a slight delay before starting the secondary or Y magnet operation. This is accomplished by counting off a pulse from the pulse generating relays by means now to be described.

When the relay APB is operated after relay .AXB operates, a circuit is closed for operating relay AYA extending from (-1-) on conductor 64, make contact of relay AGD, conductor 84. make contact of relay APB, make contact of relay AXB, break contact of relay AYB and winding of relay AYA to When relay APB is released a circuit is closed for operating relay AYB extending from (-5-) on conductor 84, winding of relay AYB, make contact and winding of relay AYA to This circuit, in addition to operating relay AYB, locks relay AYA in its operated position.

When relay APB is next operated, following the operation of relay AYB, a circuit is closed for operating the nder Y magnet YM extending from on conductor 84, make contact of relay APB, make contact oi relay AXB, make contact of relay AYB, allotter wiper AF and associated terminal, conductor 34, winding of finder magnet YM and break contact of magnet ZM to This steps the lnder in its Y or secondary direction and when relay APB is next released, this circuit is opened for releasing magnet YM. At the next energization of relay APB, magnet YM is again energized over the above described circuit for advancing the Vnder switch another step in its secondary or Y direction, after which magnet YM is released by the release of relay APB. This secondary operation of the finder switch is continued until the marked line is reached. From the above it will be apparent that relays AYA and AYB count off one pulse from the pulse generating relay APB after the termination of the X magnet operation and before the operation of the Y magnet can be effected, thus providing a delay to allow the iinder switch wipers to cease vibrating.

Since it is assumed that the third line in the third level is calling, when the nder magnet YM is energized the third time for advancing the finder switch to the third terminal, a circuit is closed for operating relay AYS for stopping the Y advance of the iinder switch. This circuit extends from (-5-) on conductor 84, upper winding of relay AYS, make contact of -relay AYA, allotter wiper AG- and its associated terminal, conductor 32, sleeve conductor IS, nder switch wiper IS Iand its associated terminal, make contact of relay OLR and winding of relay OCO to Since relay AYS has been previously primed the closure of this circuit causes it to quickly operate. Relay OCO of the calling line may or may not operate in series with the upper winding of relay AYS., but the OCO relay will be operated following the operation of switching relay SW of the finder link as will now be described. The operation of relay AYS closes a locking circuit for relay APB extending from (-H on conductor 84, make contact of relay AYS, make contact and winding of relay APB to 'I'his circuit holds relay APB operated, thus maintaining the above described 4circuit vfor magnet YM energized until relay APB is released by the release of relay AYS. The operation of relay AYS closes a circuit for Operating relay SW of the.

line nder extending from (4.-), make contact of relay SA, make contacts of the X and Y of! normal springs of the line finder in multiple', winding of relay SW, make contact and winding of relay ST to This circuit operates relay SW and locks relay ST and is effective because relay AYS opens up the circuit to on conductor 23 for removing the short circuit from the winding of relay SW. A circuit is now closed for operating magnet ARX in the A allotter extending from (-1-), make contact of relay AGD, make contact of relay AYS, conductor 54 and winding of magnet ARX to The operation of magnet ARX opens up the circuit to for relay AGD for effecting the release of this relay. With relay AGD released the circuit for relay AYS is opened by removing (-1-) from conductor 84 for effecting the release of this relay. The release of relay AGD opens up the above described circuit for magnet ARX and the A allotter switch is ladvanced to the next set :of terminals by the release of this magnet.

The operation of relay SW of the finder extends (-1) by way of conductor S to conductor IS for fully energizing relay OCO of the calling line circuit and this relay is operated and locked over a circuit including a make contact of relay OCO which bridges the make contact of relay OLR. The operation of relay OCO opens up and releases relay OLR and this relay in turn opens up land releases relay AST of the allotted. The release of relay AST `de-energizes the failure lamp and slow alarm circuit, it being assumed that relay AST was not energized long enough to permitan alarm signal from this slow operating alarm apparatus.

The release of relay AGD opens up and releases relay ASA and the release of relay AYS opens up :and releases relay APB. Since relay AGD disconnects (1) from conductor 84, the APA and APB relays are stopped. The release of relay AGD also opens up and releases relays AXA, AXB, AYA AND AYB, thus restoring the A allotter to normal. The A allotter may now be brought into use again by another call from a line in the odd level since the starting relay AST may be energized by way of conducto-r 25, -as previously described. The AGD relay may be energized to again effect the circuit operations by way of the A allotter as previously described when relay AST extends (-1-) from the A reset key to the left hand winding of relay AGD only when the AA brush of the allotter is associated with `an idle link. As the allotter is advanced over busy links, there will be a (-1) potential on the terminals to which wiper AA is connected by way of a conductor similar to conductor t4 as previously pointed out, thus preventing the operation :of relay AGD until an idle link is allotted.

When the calling party hangs up the receiver following the completion of the call, the opening up of the line circuitfeffects the release of relays CB and SA of the connector (not shown) for removing (-1) potential from the sleeve conductor S extending back through the nder to the calling line circuit. This opens up and releases cut olf relay OCO and relays SW and ST of the finder link. The release of relay ST closes a circuit for energizing release magnet ZM of the finder extending from (-1-), break -contact of relay ST, X and Y off normal contacts XON and YON in multiple and winding of magnet ZM to When the switch is released these off normal contacts are opened for de-energizing the Z magnet thus placing the finder link in its normal condition. It will be noted that magnet ZM applies (1) potential to conductor 44 for maintaining this link 'busy until the finder switch is restored to normal.

In response to a call from a line in the even level, the operation of the line relay marks the level to which level wiper IXX is connected during the advance of the line nder and extends (-1-) through one ofthe resistors 2R to IBR inclusive, depending on the level marked, to conductor 21 for operating relay BST, which is the start relay for the B allotter. The call from an even line causes the circuits of the B allotter to function in a manner similar to that above described for causing an allotted line finder to advance to the terminals of the calling line. It will be understood that all links are in one common `group served by the A and the Ballotters, with a call from a line in an odd level normally operating through the A allotter for causing any line finder in the group to seize the calling line. Furthermore, a call from a line in an even level causes the B allotter circuits to function in la similar manner for causing anV allotted nder in the common group to find the calling line. Since these two alloters may operate at the same time and since each finder can test odd levels by means of its X brush and can test even levels by mean-s of its XX brush, -a calling line in an odd level may operate a line nder fat the same time that a calling line in an even level operates another line nder, since these two lines control the finders thro-ugh separate allotters and through separate level wipers on the iinders.

In the event that a calling nder fails to stop on the marked level the switch will advance to its X overflow position and close the X-Y overflow contacts. This completes a circuit from (-1-), break contact of relay SW, make contact of relay ST, overflow contacts, conductor 2t and winding of relay OF to Relay OF operates and extends this circuit to the upper winding of relay OFP for operating this relay. Relay OFP disconnects (-1)' from conductor 6A for cie-energizing conductor 84, which in turn stops the pulse relay operation. Magnet ARX is energized over a circuit extending from (1), make conta-ct of relay AGD, conductor 53, make contact of relay OFP and winding of magnet ARX to The operation of magnet ARX releases relay AGD,-which in turn opens up and releases magnet ARX for advancing the A allotter to the next link. When the next idle link is reached, relay AGD may again be energized and the circuits function as previously explained, this time in connection with the next allotted link circuit. It will be obvious that relay ST of the first allotted nder will be released when wiper AB is `deenergized by the release of relay AGD, thus. effecting the release of the nder switch.

It will now be explained how the circuits function when a call is originated from a line in the odd leve1 handled by way of the A allotter and due to some faulty operation the circuits are not cleared out as above described, thus requiring the intervention of the B allotter for handling the call.

It will be assumed that a call originates from sub-station A associated with line #33 of Fig. 2, consequently the removal of the receiver at this sub-station operates line relay OLR for making this line busy in the :connector bank, for preparing the sleeve circuit for operating the cut off relay of this ,line when found, for marking 11 i Y thf l'velj wllicl'r7 thefline is' and for marking tue' une in the level', all ae previously deseribed. Relay AsfrY operated and locked for closing' tile circuit of tHeA A failure lamp and 'sldwalarirr Relay AST also elesee enculee for operating and locking relays Asn and AGD, `after the pulse generating relays APA and` APB are operated, all in the prei/lusl-y described mannerf.A

Relay s'r di the allotted line finder (assumed to letlie nder in Eig. 1) is operated, after which relays CB and. SAo'f the selector arel operated as before. These circuit oprations close the operating circuit fel; tue X magnet ef the allotted nuclei@- aricl in this example, it will be assumed that either the' Xv magnet or the Y magnet fail to operate fercleannge dut the allumer circuits. When the! common pickup interrupter, illustrated in thel left hand portion ofl Fig. 9- is energized, a circuit is closed for operating relay ABA which may be traced from this pickup interrupter, break 'Contact of relay` A'lFl, make Contact of relayy AS and' lowers 0f' relay ABA to Relay ABA 'closes a locking circuit for itself extending from C+) on conductor-A845 con- 'ducton 66, make contact and limiety winding of relay ABA t'o 1(4) Since itl'snssumed that the allottercircuits are not cleared out Within the predetermined time, the (-{4)- pulse applied. to common 'timerA conductor illustrated in the left Ahand portion of Fig. 9is effectiveto operate relays OFP and ATF of' the AV allottelx The circuit foroperating relay OFP may be traced from conductor- CP, make contact oi relay ABA, 'conducto'r 3R an'd'lower winding 'ot relay OFP to The circuit for operating relay ATFv may b'e traced from conductor ECP, make4 contact of rel-ay. ABA, upperv winding of relayATF, break contact f relay ATE,- conductor '48, breakfcontact 'f relay'BTF 'of the Ballotter, conductor '4 9, break contact of relay ATF.and resistor- 24R to Relay A'IFfcloses two locking circuits Afor itself) the. rst "extending through the X make contact of relay ATE- (this contact mkingebeiore any vother contacts of vthis'relayare switched) and resistor 24R to The-'second lockingv circuit extends from (Til-l, lowerbreak 'contact of the A reset key, make contact and lewruinding efrelay ATE to. When 'the Vpulse on'conkduc'tor ECP terminated, 'relayJOEP-'is v'released and the ter'- mination =of this pulse opens up the first de"- 's'cr'ib'e'd locking circuit for relay ATE, this relay now-being locked operated vby wayn ot'its second locking circuit.

The. operation of relay ATF' disconnects the common pickup conductorlfrom the operating .winding off'rclay ABA and 'the operation of relay. OFP disconnects fromfconductors and 66, thus. opening up the locking circuit for relay ABA and effecting the release of this relay. A circuitis 'now 'closedrfor operating relay XTM offFi'g. 2, extending'from E(et), make'contact of .relay JATF, conductor 35 and winding of relay 'XTM' to. Theroperation'ofrelay ATFcpens upfand releasesirelay AST Aand the operation of relay OFP disconnects C+) from cor'icluctor 64 for effecting the release of relays ASA and AGD. The.y operation of: relay OFP and 'the release of relayiAGDalso 'stopsthe vpulse generating relays LAIPA and APB, since (-1-) vis 'removed from conductors ik andv 84. Theoperation of lrelay OFP also closes. acircuit i'orenerg'izing the A'a'llotte'r stpnlagnetfextending'from C+), make contact `of relay AGD,"conductor 53-J make contact of relay OFP and Winding of magnet ARX to 1.2'` Thev release or relay AGD opens. up thisv circuit fof magnet ARX for eifecting the release of this magnet and. the advance of the A allotter to the next idle link.

It will be assumed that none of the relays AXB, AYA, AYB or AYS are operated response to this cal-l becausev of 'the faulty opera,- tion' of the A allettel" or line finder. With relay ATF energized, the A allotter is locked out of service because the operating circuit for the A allotter start relayAST is open. TheV A allottel transfer lamp. TFA is energized over a circuit extending from (4.2), n'iake contact of relay ATF, lanp TFA and conductor 43 to the delayed alarm circuit for bringing in this alarm after a predetermined time. interval.

The release of relay AGD of the A allotter ope'ns upA and releases relay ST of the :finder and this rfely in turn. eiects thev release of relays CB and SA of the finder.

It will now be explained how the B allotter takes. over and handles the call from the. calling line. in the od` level normally served by theV A allotter but now-r to. be served by the B allotter because of some circuit failure. Since the op.- eration ofthe #2 lnder failed in this example, relay SW of this finder is not operated. The op:- e'ration of relay XTM bridges the odd and even level contacts selected by the vX and XXA Wipers respectively ofr the line lnder-s. Since these level contacts are common to all line nders oi the. group. and since a line nder using its X level selecting wiper failed in this example, the next allotted line finden is controlled by way of the B allotter and the XX brushv of this line nder -for selecting the level in which the calling line is located. Theoperation or relay XTM also connects. conductors. 4.6 and 4,1 together, these lconductors being controlled toV operate they trunk start relays A'ISfand BTS respectively. The operation of relay ATF disconnects the. trunk start conductor i6 from the A Yallotter trunk start relay A'ISrandsinceacall from atrunk line. nor- Amallynsing `start conductor 46 is now controlled by way ofthe lower make contact of relay XTM forfenergizing start conductor 4l, the tru-nk start relay BTS associated with the B allotter will function to vl'landlethe call. The toll line opera.; tion will be 'described later.

The B allotter will be stepped ofi the ndei' link (if it is standing on this link at this time) by means of the circuit extending from C+), make-contact of -relay- AGD, break` contact of relay AYS, Aallotter brush AB and its `ternnlna-l, 'conductor 23, 'Bfallotter brush BB and its.r terminal, 'break contactolA relay BYS, conductor 69, make 'Contact of relay OFP, conductor 68 and winding of magnet BRX to When relay -AGD-fis released, Ylas. above described; this circuit is `opened and magnet BRX is cle-energized tovadvancethe'B allotter tothe next idle link.

I-hexB "start relay BST is now energized over acircuit'extending from (+V), make vcontact of 'line v-relay GLR, 1resistor 3R, conductor 25, break contact oivrelayfATS,'makecontact of relay ATF?, conductora, fbreak vcontact of relay BTS, lbrealfc contactfffrelay B-TF,'-nlake' contact of lrelay ATB 'andwinding of `relay BST to. lRelay BSFL1 -closes -a locking'c'ircuit for 'itself which includes itleiabove--described circuit'and the inner upper make 'contact lof'relay BST which bridges the normallyclosed make 'contact of relay ATB.

V"Relay ABSAis jnow operatedover acircuit ex'- 'froml |-;)f, :break'contactfof B reset key, conductor 6l, break contact of relay OFP, con- 13 ductor 56, make contact of relay BST, conductor 12, break contact of relay BXA, conductor 1I and winding or relay BSA to Relay BGD is now operated over a. circuit extending from (-1-), break contact of B reset key, make contact of relay BST, conductor 18, winding of relay BGD, conductor 16, make contact of relay ATB, break contact and winding of magnet BRX to It will be observed that relay BGD can only be operated when the B allotter is at rest in association with an idle link because a busy link will apply (-1-) potential by way of the terminal and wiper BA to the point between the windings of relay BGD and stepping magnet BRX for preventing the operation of relay BGD and for operating magnet BRX to drive the allotter away from this terminal. The operation of relay BGD closes a locking circuit for itself extending from (-1) break contact of the B reset key, make contact of relay BSA, conductor 14, make contact and winding of relay BGD, another make contact of relay BGD, conductor 15, break contact and Winding of magnet BRX to It will be noted that this locking circuit for relay BGD provides a means for holding this relay operated even though relay ATB is released asan indication that the last link of the group is taken for use. A locking circuit is also closed at this time for relay BSA which may be traced from (-1-), break contact of B reset key, conductor 61, break contact of relay OFP, conductor 56, make contact of relay BSA, conductor 70, make contact of relay BGD, conductor 'Il and winding of relay BSA to The operation of relay BSA connects the common pickup interrupter PU to the lower winding of relay BB'A so that this relay can be operated and locked to start the timing operation for the B allotter. This is for the purpose of providing means for operating'relay OFP in response to a pulse on common conductor ECP extended by way of conductor 3B and make contact of relay BBA to conductor 38 which extends back to the lower winding of relay OFP. Consequently, if the B allotter is not cleared out within the predetermined time in connection with this call, relay OFP will be operated and the B allotter advanced to the next link by means of a circuit extending from (-1-), make contact of relay BGD, conductor 69, make contact of relay OFP, conductor 55 and winding of magnet BRX to It will be obvious that the operation of magnet BRX eects the release of relay BGD, in the manner previously described, for releasing magnet BRX, thus advancing the B allotter to the next idle link. Relay BIF cannot be operated by way of the pulse on conductor 39 applied to its upper winding because conductors 48 and 49 are both open at this time at break contacts of relay ATF.

The pulse generating relays BPA and BPB of the allotter are now operated over circuits extending from (-1) on conductor 56 (from the B reset key), make contact of relay BGD, break contact of relay BYS, break contacts of relay BPA and :windings of relays BPA and BPB to These BPA and BPB relays go through their cycles of operations by means of circuits exactly like those above described in connection with the A allotter and, therefore, need not be described in detail.

Relay ST of the allotted line finder is operated, when relay BGD operates, over a circuit extending from (-1), make contact of relay BGD, break contact of relay BYS, B allotter Wiper BB and its terminal (assumed to be in contact with the #3 link), conductor similar to 23 and winding of a start relay similar to relay ST of the allotted line nder to The operation of the ST relay of the line nder provides the pre-impulse for operating the CB and SA relays of this link in the same manner described in connection with the #2 line finder link.

The X magnet of the allotted line i'inder is now advanced in its primary or X direction by way of a circuit which may be traced from (-1-) on conductor 56, make contact of relay BGD, make contact of relay BPB, break contact of relay BXB, wiper BD and its associated terminal, conductor similar to 33 and winding of an X magnety similar to XM of Fig. 1 to at the break contact of the associated Z magnet. This circuit functions to drive the line finder in its X direction until it reaches the marked level (assumed to be level #3), at which time relay BXA is operated over a circuit extending from (-1-) make contact of line circuit line relay OLR, make contact of relay XTM, conductor 4 associated with the third level XX brush terminals of all finders, XX brush of the operating inder, conductor similar to -conductor 28, third terminal of B allotter wiper BE. make contact of relay BGD, break contact of relay BYA and winding of relay BXA to Relay BXA closes a locking circuit for itself which may be traced from (-1-), break contact of the B reset key, conductor 67, break contact of relay OFP, conductor 56, make contact of relay BSA, conductor l), make contact of relay BGD, make contact of relay BXA, resistor 42R. and winding of relay BXA to When relay BPB is released, the X magnet of the allotted iinder is released, leaving this iinder kin association with the marked level and atthis time a circuit is closed for operating relay BXB extending from (-1-) on conductor 56, make contact of relay BGD, break contact of relay BPB, make contact of relay BXA,

break -contact and winding of relay BXB to Relay BXB closes a locking circuit for itself extending from (-1-) on conductor 56, make con.- tact of relay BGD, make contact and winding of relay BXB to Relays BYA and BYB are now operated for counting 01T a single pulse from the pulse generating relays to introduce a delay between the end of the X stepping and the beginning of the Y stepping operations to enable the nder switch wipers to settle down and stop vibrating. The circuit for relay BYA is closedby the next operation of the BPB relay after relay'BXB is operated, this circuit being traced from (-1-) on conductor 56, make contact of relay BGD, make contact of relay BPB, make contact of relay BXB, break contact of relay BYB and winding of relay BYA to Now when relay BPB next releases a circuit is closed for locking relay BYA and for operating BYB which may be traced from on conductor 56, make contact of relay BGD, winding of relay BYB, make contact and winding of relay BYA to This circuit is eii'ective because (-1-) is removed from the point between the windings of relays BYA and BYB by the release of relay BPB. The circuit for the Y magnet kof the allotted finder is now effective and maybe traced from (-1-) on conductor 56, make contact of relay BGD, make contact of relay BPB, make contact of relay BXB, make contact of relay BYB, wiper BF and third terminal, conductor similar to conductor 34, Winding of a Y magnet similar to magnet YM and break contact of a magnet similar to magnet ZM to The pulse generating relays drive the allotted under in its Y direction by means of this circuit until the terminal of the calling line is reached. at which time stop relay BYS of the B allotter is operated, it being understood that the BYS relay lwas primed when the BG relay was operated over a circuit extending from on conductor 56, make contact of relay BGD, resistor 21R and lower winding of relay'BYS to thus rendering this BYS relay very fast in its operation to stop the Y stepping when the marked line is reached. The circuit for operating relay BYS may be traced from (-l-l on conductor 56, make contact of relay BGD, upper winding of relay BYS, make contact of relay BYA, wiper BG and its-third terminal, conductor similar to conductor 32', conductor similar tol conductor IS of the allotted link, wiper similar to wiper IS of the finder and its associated terminal, make contact of line relay DLR and winding of relay GCOy to The operation of relay BYS closes a circuit for operating the switching relay of the allotted link extending from (-l-l, make contact of the SA relay ofthe selector associated vrvs/ith the allotted link, make contacts in parallel of the X and Y oil normal springs of the iinder, winding of a relay similar to relay SW of Fig. l, make contact and Winding of a relay similar to relay ST to (-il. circuit 'for operating the SW relay also completes a locking circuit for the ST relay, this operating circuit for the SW relay being ellective because (-1-)y potential isl removed from the conductor similar to conductor 23 by the operation of relay BYS and the opening of 'its lowermost. break contact, The opera-tion of the SW relay switches the circuit for the vCIB relay from the preimpulse circuit to the circuit including the calling line. 'The operation of relay BYS also closes a. rcircuit for -operating mag-net BRX extending from (-1-), make contact of relay BGD, make contact of relay BYS, conductor `68 and winding-of magnet BRX tol (-0. The operation of magnet opens up the energizing circuit of relay BGD, for eiecting the release of this relay. The operation of relay SW of the :finder eiects the release of relay BYS by the application of' (-4-): to. aV conductor similarl to conductor 11 whichy extends though the terminal` and wiper onf the B1 allotter to the upper windingof relay Bln-'Sfar .short-crcuiting this winding and effecting the release of the relay. It will he understood that, relay BYS will not remain operated over the circuit including resistor 21R and its lower winding, but even though this relay does remain operated over this circuit it will be released when relay BGD releases for disconnecting conductors-.lili` from resistor" 21R, conductor 55 beingv connected to potential. yThe release of: relay BGDy opens up the above described circuit; tomagnet BRX for effecting the release ci this; magnet .and the consequent advance of the B allotter to the-next idle link, assu-medv tobe link M It: will be obvious Vthat there will: be an operating circuitY for the BRX' magnet by way loi busy terminals and: brush BA for advancing lthe Bailotterfto the nrstidle link, this operating circuit from (-l-lk onthese busy terminals also functioning to prevent operationv of relay until the idle is reached.

Referring backto the `operation of relay BYS, a locking circuit. isprov-ided forarelay BPB, which may bey traced from (+3 on conductor 5G, make contact of relay BGD..makecontactofre1ay:BYS-g make contact and winding of relay BPB to When relay BYS is released, this locking circuit for relay BPB is opened for eiecting the release of this latter relay, since relay BGD will be released at this time for disconnecting the on conductor 56 from the operating circuit of relay BPB. 'The release of relay BGD opens up and releases relays BSA, BXA, BXB, BYA and BYB. The release of relay BGD also removes the (--l potential on conductor 55 from the operating circuit of the BPA and BPB relays for preventing the further operation of these relays.

The cut off relay of the calling line is operated by the operation of the SW relay of the line finder over a circuit which may be traced from make contact of the SA relay of the selector, make contactV of the SW relay of the finder, a

conductor similar to conductor l S, the S wiper of the line nder and the terminal to which it is connected, make contact oi relay OLR and winding of relay OCO to Relay OCO closes a Contact in parallel with the make Contact of relay OLR for providing a locking circuit for the OCD relay, after which relay OCO opens up and releases relay OLR. The release of OLR disconnects A({-) potential from the circuit leading through resistor 3R, and conductor 25 and thence by way of a make contact of relay BTF to conductor 2l, break contact of relay BTS, break contact of relay BTF, makey contactand winding of relay BST to for eiecting the release of relay BST. This places the B allotter in its normal condition.

When the calling party hangs up, relays CB and SA of the link circuit in use are released for disconnecting (-i-i potential from the holding sleeve for in turn effecting the release of relays OCO, ST' and SW. The connector and selector c'ucuits. (not shown) are released in the wellknown manner and the finder is released by the release. of relay ST closing an energizing. circuit for the release magnet of the fmder, thus restoring thev link equipment. to normal.

From the above description it will be seen that when an allotter is timed out, no nder of the group is locked out.A This time out operation simply slows up the operation. of the complete group because normally two originating calls in the group, one in an odd level and one in an even level, will function through the .A and B allotters to cause two line nders to simultaneously hunt. The time out operation causes the control to be effected by one allotter only for lines in both the odd and even levels, thus permitting onlyv one line Vfinder operationv to be eflective in the complete group at any one time. It will also be seen that a: start condition from a line in an odd level normally operates through the A allotter and anynder X brush to find the level in which the calling line is located that a start. condition from a line in an even level operates .through the B allotter and any lnder XX brush to control thefindi-ng. operation to this line. Furthermore, theabove description. explains how the time out operation of the A allotter functions to bridge: thev odd and even level terminals of` all line finders of the groupso that the XX brush of any linder functions by Way of the B-allotter for linding the. calling linein either an odd or an even level. Likewise, if the B allotter istirned out, these odd and even level marking terminals are bridged andany line'nderwill., have itsinding operation controlled by way of .its X. brush and the Aallotter for :Ending a line in an Iodd level or a line-in an even level.` It hasr :also been pointed out how, if a time out operation is effective for locking out one allotter, the failure of the companion allotter or a iinder allotted thereby simply causes this allotter to take another step and allot another finder link.

In the event that all finder links of a group are busy at any one time, common conductor 45 is de-energized for effecting the release of relay ATB. Under this condition, the removal of the receiver at a calling sub-station will operate the associated line relay over a circuit including common conductor 29 and the winding of the induction coil LBT. The (-1-) potential applied to common conductor 25 by the operation of a line relay under this condition is ineffective to operate the start relay, for example relay AST of the A allotter, because it is open at a make contact of relay ATB. In the eventk that the A allotter has been timed out, the BST relay cannot be operated under this condition because the winding of this relay is likewise open at a normally closed (now open) make contact of the ATB relay. The calling party hears the busy tone under this condition over a circuit which may be traced from the source of busy tone in the upper portion of Fig. 3, condenser, break Contact of relay ATB, winding of coil LBT, break contact of relay AGD, conductor 4B and break contact of relay BGD to (-1-), this tone inducing a similar tone in the winding of the induction coil LBT to which the calling line is connected.

It will now be explained how the circuits function when additional lines are connected to the 11th sets of Y terminals, it being understood that these lines may be provided in exchanges where the regular 100 line group is not suilcient to take care of all subscribers. It has been explained how the relays OF and OFP of the A allotter are operated when a line finder goes to its X overflow position, for clearing out the circuits. In systems where the 11th or Y overflow terminals are not used, these OF and OFP relays are similarly operated when a line finder goes to its Y overflow position for clearing out the circuits and assigning another line nder. It will be obvious that any line finder of the group causes this overflow operation because common conductor 24 leading to the OIF and OFP relays is energized by the closure of the X-Y overflow contacts of any finder.

It will now be assumed that there is a line connected to the bank terminals associated with the 11th Y step of the 3rd level in the line nders and that a call is initiated from this line. Consequently, the circuits will be operated in the previously described manner for causing the illustrated line finder to go to the third level, after which it will be driven over the bank terminals in this level, all as previously described. In this example, the X-Y overflow contacts are operated when the line finder takes its 11th Y step. Since relay ST of the line finder is energized and since relay SW of the line finder is not energized at the time of this 11th step, conductor 24 is energized for energizing relay O-F of Fig. 4. This latter relay is slow to operate and it may be as slow as desired by using a dashpot relay. Since there is a substantial interval of time introduced between the closure of the overflow contacts and the extension of energized conductor 2d to the upper winding of relay OFP, this delay permits relay AYS of the A allotter to operate for operating relay SW of the line finder, for extending the link to the calling line and for clearing out the allotter, all in the above described manner. It will be `understood that,

should the line linder fail to switch through to the line associated with the 11th Y step, relay OF will have sufcient time to operate and extend the connection to relay OFP for clearing out the allotter and finder circuits used and for allotting another finder link. It will also be understood that, should there be no line connected to the 11th Y step, these OF and OFP relays will function in the above described manner for clearing out the allotter and the line nder circuits and for allotting another finder link.

It will now be explained how the circuits function in response to a call from a line (toll line for example) located in the normal level of the finder switch banks. It has previously been pointed out that the system may operate with l0 or Il lines in each level. This is also true for the normal level of each nder, with an allotted finder operating only in its Y or secondary direction for selecting l0 or Il lines in the normal level. It is proposed to stagger the line control circuits in the normal level so that odd numbered lines in this level operate through the A allotter to cause a finder to select an odd calling line and arranged for operation through the B allotter for causing selection of even lines in the normal level. These normal level lines are staggered as indicated in Fig. 8 and, since the A and B allotters have separate control circuits and since odd :and even numbered toll lines operate through these separate allotters, two calls may be simultaneously handled from the normal level if one of these calls is from an odd numbered line land the other is from an even numbered line.

I When an odd calling toll line circuit is closed the line relay, similar to relay OLR of Fig. 2, is operated and this relay, as well as rall oddV line relays in the normal level, applies (-1-) to the conductor leading to resistor 2BR in the lower left-hand corner of Fig. 2. This conductor does not connect to a terminal of a level selecting brush, such as brush IX, since the allotted nder does not operate in its X direction from a call of this class. (-1-) is therefore extended through resistor l28B., conductor 4B, break contact of relay AI'F, conductor 5l, make contact of relay ATB, conductor 52 and winding of relay ATS to Relay ATS rapplies (-1-) potential to the A start failure lamp ASTFL for operating this lamp and bringing in the alarm ifthe circuits do not function properly to clear out, all as described above. It will be pointed out at this time that the calling toll lines have preference over calling local lines because the operation of relay ATS will effeet the operation-of relay AXB (as will be later described) to open up the circuit through allotter brush AD and conductor 33' leading to the X magnet of the allotted finder to prevent the operation of the X magnet on a call of this class. Relay ATS also opens upon common start conductor 25, thus preventing the operation of relay AST to mark a call from a local line.

Relay ATA is now operated over a circuit extending from (-1-), break contact of the A reset key, break contact of relay ASA, make contact of relay ATS and winding of relay ATA to Relay ATA closes a locking circuit for itself extending from (-1-), make contact of relay ATS, make contact and Winding of relay ATA to A circuit is now closed for operating relay AST extending from (-1-), resistor 13R, make contact of relay ATA, make contact of relay ATS, break contact of relay ATF, conductor 5l, make contact of relay ATB, conductor 59 and winding of relay AST to Relay AST closes a locking circuit for itself extending from (-1-), resistor I 3R, make contact of relay ATA, make contact of relay ATS, break contact of relay ATF, make contact and winding of relay AST to A circuit is now closed for operating relay ASA extending from (-1-), break contact of the A reset key, break contact of relay OFP, make contact of relay AST, conductor BI, break contact of relay AXA, -conductor 60 and Winding of relay ASA to Relay ASA closes a locking circuit for itself (being completed when relay AGD is operated as will next -be described), extending from (-1-), break contact of the A reset key, break contact of relay OFP, make contact of relay ASA, conductor 58, make contact of relay AGD, conductor 6I) and winding of relay ASA to Relay AGD is operated over a circuit extending from (-1-) break contact of the A reset key, make contact of relay AST, conductor B5, winding of relay AGD, make contact of relay ATB, conclue-l tor 55, break contact and winding of magnet ARX to Relay AGD closes a locking circuit for itself extending from (-1-), break contact of the A reset key, make contact of relay ASA, conductor 63, make contact and winding of relay AGD, another make contact of relay AGD, conductor 55, break contact and winding of magnet ARX to Relay AGD closes circuits for causing the pulse generating relays APA and APB to go through their cycles in the previously described manner. The operation of relay AGD also closes the previously described circuit for operating relay ST of the allotted line iinder, this circuit extending from (1), make contact of relay AGD, break Contact of relay AYS, wiper AB and its associated terminal, conductor 23 and winding of relay ST to Magnet XM of the (allotted nder does not operate in this example, -but relay AXB does operate over a circuit extending from break contact of the A reset key, break contact of relay OFP, conductor `(54, make contact of relay AGD, conductor l84, conductor 66, make contact of relay ATA, conductor 62 and winding of relay AXB to Relay AXB closes a locking circuit for itself extending from (-1) on conductor 84, make contact and winding of relay AXB to Relay AYA is now operated over a circuit extending from (-1-) on conductor 84, make contact of relay APB, make contact of relay AXB, break contact of relay AYB and winding of relay AYA to This circuit for relay AYA is effective only when relay ABP is operated. When relay ABP next releases, relay AYB is operated and relay AYA is locked operated over a circuit extending from (1-) on conductor 84, winding of relay AYB, make contact and winding of relay AYA to This operation of the AYA and AYB relays does not perform the saine function previously described, that is, introducing a delay between the X and Y operations because there is no X operation in this example.

The operation of relay ST of the allotted nder completes the previously described pre-impulse circuit for eiecting the operation of relays CB and SA of the iinder. The nder switch Y magnet now advances the iinder lswitch in the Y direction over a circuit extending from (1-) on conductor 8S, make Contact of relay APB, make contact of relay AXB, make contact of relay AYB, wiper AF and its associated terminal, conductor 34, winding of Y magnet'and break contact of magnet ZM to The pulse generating relay APB provides pulses for stepping the Y magnet until the iinder reaches the marked line, at which time relay AYS will be operated, this latter relay being primed by the operation of relay AGD to make relay AYS fast operating. This priming circuitmay be traced from (-1) on conductor 84, resistor I'IR and lower Winding of relay AYS to this circuit preventing sufcient current now to operate the AYS relay.

When the allotted iinder reaches the terminal of the calling line, a circuit is closed for fully energizing relay AYS, this circuit extending from (-1-) on conductor 84, upper winding of relay AYS, make contact of relay AYA, Wiper AG and its associated terminal, conductor 32, conductor IS, wiper IS of the finder and its associated terminal, make contact of the line relay of the calling line and winding of the cut ofi relay to The operation of relay AYS closes a circuit for locking relay APB extending from (-1-) on conductor y84, make contact of relay AYS, make contact fand winding of relay APB to A circuit is closed at this time for operating relay SW of the nder extending from (1), make contact of relay SA, conductor S, Y ofi normal contact YON, winding of relay SW, make contact and winding of relay ST to This circuit also locks relay ST operated and is effective because conductor 23 is de-energized by the opening of the lowermost break contact of relay AYS.

Magnet ARX is now energized over a circuit extending from (-1-), make contact of relay AGD, make contact of relay AYS, conductor 54 and winding of magnet ARX to The operation of magnet ARX opens up and releases relay AGD and the release of relay AGD opens up and releases magnet ARX, thus advancing the A allotter to the next idle link. The operation of relay SW of the finder completes the circuit for operating the cutoff relay of the calling line extending from (,-1-), make contact of relay SA, conductor S, make contact of relay SW, lconductor IS, finder switch wiper IS and its associated terminal, make contact of the line relay and the winding of the cut oil relay to The operation of the cut off relay opens up and releases the line relay which in turn removes (-1) potential from the circuit including resistor 28R and conductor 45 for effecting the release of relay ATS. Relay AYS is released, either by the short circuiting of its upper winding when (-1-) is applied to conductor 32 by the operation of relay SW, or when relay AGD is released for removing (-1-) from conductor 84.

The release of relay ATS opens up and releases relays ATA and AST. The release of relay AST opens up and releases relay ASA. The release of relay AGD opens up and releases relays AICB, AYA and AYB and the pulse generating relays are stopped by the de-energization of conductor 84 by the release of relay AGD. This places the A allotter in condition for handling the next call, the calling line circuit now being extended to the windings of the CB relay of the selector by way of make contacts of relay SW and the IT and IR brushes of the line nder.

It should be mentioned at this time that the operation of relay AGD closes a circuit for kicking the B allotter oi this finder link (if on this link), this circuit extending from (1-), make contact of relay AGD, wiper AA and its associated terminal, conductor 44, terminal and wiper BA of the B allotter. break contact of relay BGD.

21 conductor 1B, make contact of relay ATB, break contact and winding of magnet BRX to When the circuit of the calling line is opened to release the connection, potential is removed from sleeve conductor S for effecting the release of relays ST and SW of the line finder. The line finder switch is now released by means of its Z magnet over a circuit extending from (-H, break contact of relay ST, Y off normal contact and winding of magnet ZM to It is believed that the above explanation of a call from a toll line and the previous explanation of how the B allotter functions to step in and handle calls normally handled by way of the A allotter, when the call through the A allotter fails, is suflicient to indicate how these toll lines are similarly handled by the A allotter under normal conditions and by the Ballotter under trouble conditions. It is not believed necessary to explain in detail how a regular line in an even level or an even numbered toll line causes the operation of a line circuit, similar to that connected to substation B of Fig. 2, for causing the B allotter to normally handle the call and for calling in the A allotter in the event that a trouble condition prevents the extension of the connection by Way of the B allotter.

In the event that the calling toll line is an even numbered line, the operation of the line relay associated with this line circuit applies (-1-) to the conductor leading to resistor 3BR the circuit then extending through this resistor, conductor 41, break contact of relay BTF of the B allotter, make contact of relay ATB and winding of relay BTS to Current in this circuit operates relay BTS for effecting control of one of the line finders of the common group, this control being by way of allotterB because this is an even numbered toll line. In the event that 11 toll lines are associated with the normal level of the finder switch multiple, a call from the 11th line in this level will cause the allotted line finder to advance to the 11th terminal and, although the Y overflow contacts are closed at this point, the slow operating OF relay will permit the switching through of the finder to the calling line before relay OFP operates to clear out the connection and transfer to the next finder. This operation has previously been described in connection with a call to a local line which advances the allotted finder to the 11th point.

Referring to Figs. 1 and 2, it will be seen that each line finder has a fourth wiper connecting to a fourth terminal at each line multiple, this wiper being indicated IHS for the first line finder and ZI-IS for the second line finder. This fourth conductor is for supervisory, metering, restricted service marking or the like, the circuits ofthis fourth conductor not being shown in the present disclosure since these circuits may or may not be used and form no part of the present invention.

Having described an automatic telephone system as particularly adaptable for use in connection with the line finder type of system controlled by a dual allotter arrangement, it is desired to have it understood that this form is selected to facilitate in the disclosure of'the invention rather than to limit the number of forms which it may assume; and it is to be further understood that various modifications, adaptations and alterations may be applied to the specific form'shown to .meet the requirements of practice, without in any manner departing from the spirit orlscope of the invention except as limited by the appended claims. What I claim is:

l. In a telephone system; two groups of lines; a control equipment for each group, each control equipment being normally controlled only from its associated'group of lines; a group of line finders, each finder having access at all times to all of said lines; means responsive to a calling conditionon any of said lines and the operation of the control equipment associated with that line for operating any one of said line finders to seek said calling line; and means for transferring the control equipments from one to the other of said groups of lines for operating any one of said line finders.

2. In a telephone system, a group of lines divided into first and second groups, a finder switch having access tov all of said lines, said finder switch having first and second wipers means responsive at all times to a call from a line in either of said groups for starting said finder searching for the calling line, and means controlled by said first and said second wipers for causing said finder to seize lines in said first and said second groups respectively.

3. In a telephone system, a group of lines `divided into first and second groups, means for initiating a call on any of said lines, a nder switch having access to. all of said lines, said finder switch having first and second wipers, means responsive at all times to the initiation of a call from a line in either of said groups for p starting said finder searching for the calling line, means controlled by said first and said second wipers for causing said finder to seize lines in said iirst and said second groups respectively, and transfer means for causing said finder to seize any calling line irrespective of its group, said means comprising only one of said wipers.

4. In a telephone system, a group of lines divided into first and second groups, means for initiating a call on any of said lines, a plurality of finder switches having access to all of said lines, said finder switch having first and second wipers, means responsive at all times to the initiation of a call from a line in either of said groups for starting any one of said finders searching for the calling line, means controlled by said first and said second wipers for causing the associated finder to seize lines in said first and said second groups respectively.

5. In a telephone system, a plurality of groups of lines, an automatic switch having directive primary and secondaryk movements, a plurality of wipers positioned by said two movements, a first and a second auxiliary wiper positioned by `said primary movement alone, and first and second control means including said first and Asaid second auxiliary wipers respectively for determining the group of lines to be selected by said plurality of wipers.

6. In a telephone system, a plurality of groups of lines, an automaticY switch having directive primary and secondary movements, a'. plurality `.of wipers positioned by said two movements, a

first and a second auxiliary wiper positionedby said primary movement alone, first and second control means including said first and said second auxiliary wipers respectively for deter'- mining the group of lines to be selected by said plurality of wipers, and time controlled-means causing either said first or said second control -means to determine the group offlin'es to be selected by said plurality of wipers.v 'i

v#Lyin `a telephone system, a plurality o f step-,- by-step line .nnders each operated -in a `primary movement and in a secondary movementby primary indiv-secondary stepping magnets respectively in the associated finder, a common allotter.h for allotting nders for use, a pulse generating relay in said allotter for operating said primary and said secondary stepping magnets of any allotted one of said line finders, another relay having a slow-to-releasecharacteristic, means for adjusting the length ofA the releasing period of said another relay, and means utilizing the last-mentionedmeans for determining the rate of operation of said pulse generating relay.

8.- In a telephone system, a group of line y finders each having a primary and a secondary hunting movement, a primary test wiper for each finder, counting relays common to all of said findersQmeans for initiating the primary hunt-l ingV movement of an idle one of said finders, means responsive to the primary test wiper of said finder encountering a predetermined potential for stopping the primary hunting movement of said finder and for causing the operation o said counting relays to measure off a predetermined time interval. and means responsive to. said operation of vsaid counting relays for initiating the secondary hunting movement of said finder, A

9` Inf a telephone system, a group of line finders each having a primary and a secondary hunting'movement, a primary ktest wiper for each finder, pulse generating relays common to all'oi said finders, counting relays common to all of said nders, means responsive to a call for caus-x ing said pulse generating relays to generate pulses, means responsive to said call for temporarily associating said pulse generating relays and said counting relays with any one of said finders, circuits controlled by said pulse generate ing relays for operating said one finder in its primary and secondary hunting movements, and circuits controlled byv said counting relays for changingsaid one finder from its primary hunting movementto its secondary hunting movement.`

10. In a telephone system, two groups of lines, one group of nder switches having access to lines in said two groups', means for operating one of said switches to cause it to search for one calling line in onel of said two groups, means controlled by the initiation of a call from another line in the other of said two groups 4While said one switch is stillsearching for said one line for initiating the operation of another of said fifi switches before said one switch iinds said one line, and timing means controlled by a previous call for preventing the operation of said other switch until -saidnone switch nds said one calling line.

11. In a telephone system, a group of subscribers lines divided into first and second subgroups, a plurality of toll lines, a finder switch having accessto all of said lines and having first and 'second wipers, means responsive to a call from a toll line or a subscrihers line in any of the. respective sub-groups for starting said finder searching for the calling line,V means including said rst wiper for causing said finder to seize said calling line when saidcalling line is in the first subscriberts sublgroup, means .including said second wiper for causing said nder to seize said calling line when saidV calling line isin the; second 'euh-grouper subscribers lines, and means independent of saidvwipers .for causing said' iinder lto 24 seize said calling line when said calling line is a toll line.

.12. In a telephone system; a group of lines; .a group of iinders having access to said lines; means including an allotter for allotting an idle yone of said iinders; means in said allotter responsive to the initiation of a call on any one of said lines for initiating the operation of said .allotted nder; means including a stepping relay in said allotter for operating said finder to iind the calling line; overiiow contacts closed at an overflow step of said finder; a switch-through relay in said nder; line terminals selected at said overflow step, which terminals may or may not be connected to a line; means responsive to the selection of said line terminals when they are not connected to a line and including said overow contacts for releasing said finder, for preventing the operation of said switch-through relay and for allotting another idle finder; and means responsive to the selection of said line terminals when they are connected to a line for preventing the release of said finder, for eiecting the operation of said switch-through relay and :for allotting another idle finder.

13, In a telephone system, subscribers lines, a distributor switch having a plurality of wipers, a plurality of contact sets accessible to said distributor switch wipers, a finder switch associated with each of said Contact sets and having a plurality of wipers, a trunk line individual to each finder, switching through means in each nder for connecting the associated trunk line by way of said iinder wipers to a calling subscribers line, means for stepping said distributor switch wipers over contact sets for selecting an idle finder, means for stepping the wipers of a selected nderover contacts sets for selecting a calling line, a time measuring device, means including said time measuring device operated after the selected iinder wipers have been stepped to the last contact set of the group for releasing said selected iinder and for allotting another iinder for selecting said calling line, and means operated after the selected nnder wipers have been stepped to the last contact set of the group for selecting a calling line and for allotting another iinder for a succeeding call.

14. In a telephone system, a iinder switch having a normal level and a plurality of oir-normal levels, lines of a first class terminating in said oli-normal levels, lines of a second class terminating in said normal level, means for initiat- 'ing calls from lines of said rst and said second classes, common means for directively operating said switch in two directions to select any one of said lines of said iirst class and in only one direction to select any one of said lines of said second class, means for causing said iinder to connect with calling lines of said iirst and said second classes, and means responsive to simultaneous calls from lines of each class for giving preference to calls initiated from lines of said second class.

15. In a telephone system, a iinder switch havingv a normal level and a iplurality of oir-normal levels, lines of a rst class terminating in said off-normal levels, lines of a second class terminating in said normal level, means for initiating calls from lines of said first and said second classes, common means for directively operating said switch in a primary and a secondary direction to select any one of said first class lines and only in a secondary direction to select any one Ao fsaidsecond class lines, means for causing said 

